U.S. patent number 5,656,782 [Application Number 08/449,104] was granted by the patent office on 1997-08-12 for pressure sealed housing apparatus and methods.
This patent grant is currently assigned to The Foxboro Company. Invention is credited to John P. Angelosanto, Edwin L. Karas, Simon Korowitz, Roger E. Powell, II.
United States Patent |
5,656,782 |
Powell, II , et al. |
August 12, 1997 |
**Please see images for:
( Certificate of Correction ) ** |
Pressure sealed housing apparatus and methods
Abstract
A selectively pressured housing apparatus comprising a body, a
wall member, an aperture, and a mounting seat. The body has a
chamber therein extending along a first axis, is open at a first
axial end and a second axial end, and has a port extending along a
second axis transverse to the first axis. The port communicates
with the chamber. The wall member is inside of the body and extends
transverse to the first axis and parallel to the second axis and
divides the chamber into first and second compartments, axially
spaced along the first axis. The port communicating with the
chamber is in the second compartment. The aperture extends through
the wall member and connects the first and second compartments. The
mounting seat is on the wall member and extends circumferentially
about the aperture for removably and replaceably seating an element
with a selected pressure seal to the wall member. According to one
preferred embodiment, the first and second compartments are
employed for housing process electronics associated with a
differential pressure transmitter.
Inventors: |
Powell, II; Roger E. (North
Smithfield, RI), Korowitz; Simon (Sharon, MA),
Angelosanto; John P. (North Attleboro, MA), Karas; Edwin
L. (Mansfield, MA) |
Assignee: |
The Foxboro Company (Foxboro,
MA)
|
Family
ID: |
23782876 |
Appl.
No.: |
08/449,104 |
Filed: |
May 24, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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32041 |
Dec 6, 1994 |
Des. 366000 |
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Current U.S.
Class: |
73/756 |
Current CPC
Class: |
G01L
19/14 (20130101) |
Current International
Class: |
G01L
19/00 (20060101); G01L 19/14 (20060101); G01L
007/00 () |
Field of
Search: |
;73/706,708,718,721,727,756,861.47 ;137/84 ;361/18,816 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Dombroske; George M.
Assistant Examiner: Oen; William L.
Attorney, Agent or Firm: Lahive & Cockfield, LLP
Parent Case Text
REFERENCE TO RELATED PATENTS
This application is a continuation-in-part of U.S. patent
application Ser. No. 29/032,041, filed Dec. 6, 1994, now U.S. Pat.
No. 366,000 entitled "Pressure Housing." The above cited patent
application, assigned to a common assignee, The Foxboro Company,
Foxboro, Mass., is incorporated herein by reference.
Claims
Having described the invention, what is claimed as new and secured
by Letters Patent is:
1. Selectively pressure sealed housing apparatus for electrical
elements, said housing apparatus comprising
A. a body having a chamber therein extending along a first axis,
said body being open at a first axial end and a second axial end,
and having a port extending along a second axis transverse to said
first axis, said port communicating with said chamber,
B. a wall member inside said body extending transverse to said
first axis and parallel to said second axis and dividing said
chamber into first and second compartments axially spaced along
said first axis, said port communicating with said chamber at said
second compartment,
C. an aperture extending through said wall member and connecting
said first and second compartments, and
D. a mounting seat on said wall member and extending
circumferentially about said aperture for removably and replaceably
seating an electro-mechanical fitting with a first pressure seal to
said wall member.
2. Housing apparatus according to claim 1 in which said mounting
seat projects axially along said first axis into said first
compartment from said wall member and forms, in said first
compartment, a channel having a depth extending along said first
axis and extending circumferentially around said mounting seat.
3. Housing apparatus according to claim 1 further comprising means
forming, in said first compartment, a wire-receiving channel having
a depth extending along said first axis and extending
circumferentially around said chamber.
4. Housing apparatus according to claim 1 in which said mounting
seat includes a planar surface facing along said first axis into
said first compartment for removably and replaceably seating said
element with said first pressure seal to said planar surface.
5. Housing apparatus according to claim 1 in which said mounting
seat includes a finished surface for removably and replaceably
seating said element with said first pressure seal to said finished
surface.
6. Housing apparatus according to claim 5 in which said mounting
seat is adapted for mounting said element, with said first pressure
seal, by way of said first compartment, and in which said element
is disposed in said first compartment when mounted.
7. Housing apparatus according to claim 1 in which said mounting
seat further includes fastening threads for said removable and
replaceable mounting of said element to said mounting seat.
8. Housing apparatus according to claim 1 in which at least one
axial end of said body is threaded for removable and replaceable
assembly with an end-cap for selectively closing said one end of
said body.
9. Housing apparatus according to claim 8 further comprising
A. a threaded end-cap for removable and replaceable assembly with
said one end of said body for forming a second pressure seal
between said cap and said one end, said end-cap having a
substantially cylindrical outer surface with radial recesses
therein circumferentially spaced about said outer surface, and
B. a stem threadably mounted on said body, and having
axially-spaced first and second portions for selectively engaging
said first portion in one said radial recess of said end-cap for
precluding rotation of said end-cap relative to said body.
10. Housing apparatus according to claim 9 further comprising means
for precluding said stem from rotating to disengage said first
portion from said one radial recess.
11. Housing apparatus according to claim 9 further comprising
A. a threaded aperture for receiving said stem, said threaded
aperture being located adjacent said one end of said body and
extending axially along an axis parallel to said first axis,
wherein said stem mounts in said threaded aperture so that said
first portion of said stem protrudes from said threaded aperture
and selectively engages one said radial recess in said end-cap, and
said second portion threadably seats within said threaded aperture,
and
B. a passage extending radially through said threaded aperture for
threading a filament there through to engage said second portion to
preclude removal of said stem from engagement with a radial recess
of said end-cap.
12. Housing apparatus according to claim 1 in which said port
includes a collar on said body and extending along said second
axis, said collar having a through passage communication with said
second compartment, said collar having a tubular outer surface for
seating a label and having radial projection for fixing a
rotational position of said label.
13. Housing apparatus according to claim 12 in which said tubular
outer surface has a radial recess for interfitting with and seating
said label.
14. Housing apparatus according to claim 12 further comprising a
label mounted about said collar and having a notch seated on said
radial projection for fixing the rotational position of said
label.
15. Housing apparatus according to claim 12 further comprising a
label having fastening means for removably and replaceably
fastening said label to said tubular outer surface of said
collar.
16. Housing apparatus according to claim 1 further comprising an
electro-mechanical terminal-block fitting removable and replaceable
relative to said first compartment by way of said first open end
and having a mounting portion for removably and replaceably seating
with said mounting seat, for selectively mounting said
terminal-block fitting relative to said wall member with said first
pressure seal between said first and second compartments.
17. Housing apparatus according to claim 16 in which said
terminal-block fitting includes a selected set of first electrical
terminals arranged for removable and replaceable connection, with
electrical conductors, from said first compartment when said
terminal-block fitting is mounted to said wall member.
18. Housing apparatus according to claim 17 in which said
terminal-block fitting includes a selected set of second electrical
terminals in electrical circuit communication with said first
electrical terminals and arranged for removable and replaceable
connection from said second compartment when said electrical
terminal-block fitting is mounted to said wall member.
19. Apparatus according to claim 18 in which said terminal-block
fitting spans said aperture in said wall member when mounted to
said wall member and has a planar annular surface that forms said
mounting portion, and in which said second electrical terminals are
located within said annular surface.
20. Apparatus according to claim 15 in which said mounting seat
includes a planar surface facing along said first axis into said
first compartment for removably and replaceably seating said
terminal-block fitting with said first pressure seal to said planar
annular surface.
21. Apparatus according to claim 15 in which said mounting seat
further includes fastening threads for said removable and
replaceable mounting of said terminal-block fitting, and said
mounting portion of said terminal-block fitting includes a
plurality of apertures for axial alignment and mounting engagement
with said fastening threads.
22. Housing apparatus according to claim 16 in which said
terminal-block fitting includes,
A. a terminal block having first and second opposed sides with a
selected set of first electrical terminals arranged on said first
side, and
B. a printed circuit board having first and second opposed sides,
said first side of said printed circuit board mounting iaid second
side of said terminal block and having means for electrical
connection to said first electrical terminals, said second side of
said printed circuit board having a selected set of second
electrical terminals in electrical circuit communication with said
first electrical terminals.
23. Housing apparatus according to claim 1
A. in which said body forms said second compartment with a tubular
wall extending axially along said first axis to said second end of
said body, and
B. further comprising a second mounting seat in said second
compartment for removably and replaceably mounting a second element
with a second pressure seal to said second mounting seat to divide
said second compartment into a first cavity containing said port
and a second cavity.
24. Housing apparatus according to claim 23 in which said second
mounting seat comprises a radial shoulder projecting radially
inward from said tubular wall, and a smooth inner surface on said
tubular wall extending circumferentially around said second
compartment and extending axially along said. first axis from said
shoulder toward said second end of said body.
25. Housing apparatus according to claim 23 in which said second
mounting seat comprises at least one threaded fastening member for
said removable and replaceable mounting of said second element to
said second mounting seat.
26. Housing apparatus according to claim 1
A. in which said body forms said second compartment with a tubular
wall extending axially along said first axis to said second end of
said body,
B. further comprising a second mounting seat in said second
compartment for removably and replaceably mountingly seating a
second element with a second pressure seal to said second mounting
seat to divide said second compartment into a first cavity
containing said port and a second cavity, and
C. further comprising a first circuit assembly removable and
replaceable relative to said second compartment by way of said
second open end and having a mounting portion removably and
replaceably seated with said second mounting seat, for selectively
mounting said first circuit assembly relative to said second
mounting seat with said second pressure seal between said first and
second cavities.
27. Housing apparatus according to claim 26
A. in which said first circuit assembly and said second mounting
seat engage to form said second pressure seal, and
B. further comprising an electro-mechanical terminal-block fitting
removably and replaceably seated with said mounting seat for
selectively mounting said terminal-block firing relative to said
wall member with said first pressure seal between said first and
second compartments, and wherein said first pressure seal has a
selected greater pressure strength than said second pressure
seal.
28. Housing apparatus according to claim 23
A. in which said second mounting seat comprises at least one
threaded fastening member for said removable and replaceable
mounting of said second element to said second mounting seat,
and
B. further comprising a first circuit assembly removable and
replaceable relative to said second compartment by way of said
second open end and having a mounting portion including a plurality
of through apertures for axial alignment with said fastening member
for mounting said first circuit assembly to said second mounting
seat.
29. Housing apparatus according to claim 27 further comprising
fastening means for removably and replaceably fastening said first
circuit assembly to said fastening member by way of said through
apertures to realize said second pressure seal between said first
and second cavities, and wherein said fastening means releases said
pressure seal by way of said through aperture, upon being
unfastened from said fastening member.
30. Housing apparatus according to claim 26 in which said first
circuit assembly comprises
A. a mounting bezel having first and second opposed sides and a
through aperture between said first and second sides, said first
side including at least one axial projection located on the
periphery of said through aperture and extending along an axis
normal to said first side, and adapted as a finger grip for removal
and installation of said second circuit assembly by way of said
second open end,
B. a display mounted to said second side of said mounting bezel and
visible from said first side by way of said through aperture,
and
C. at least one primed circuit board mounted on said second side of
said mounting bezel and in electrical communication with said
display.
31. Housing apparatus according to claim 30
A. further comprising an electro-mechanical terminal-block fitting
having a mounting portion for removably and replaceably seating
with said mounting seat, said terminal-block fitting including
first electrical terminals accessibly disposed in said first
compartment when said terminal-block fitting is mounted to said
wall member, and
B. said printed circuit board of said first circuit assembly
includes a set of electrical terminals for removable and
replaceable connection with said set of first electrical terminals
of said terminal-block fitting.
32. Housing apparatus according to claim 26 in which said first
circuit assembly includes
A. a mounting housing having first and second opposed sides, said
first side having at least one axial projection accessible as a
finger hold for installation and removal of said first circuit
assembly relative to said second compartment by way of said second
open end, said second side having a plurality of mounting supports
projecting axially from and spaced along the periphery of said
second side and each having one or more lateral slots and
B. at least one printed circuit board adapted to interfit with and
seatingly engage one said slot in each said mounting support to
seat said circuit board in said mounting housing.
33. Housing apparatus according to claim 32
A. further comprising an electro-mechanical terminal-block fitting
removable and replaceable relative to said first compartment by way
of said first open end and having a mounting portion for removably
and replaceably seating with said mounting seat, for selectively
mounting said terminai-block fitting relative to said wall member
with said first pressure seal between said first and second
compartments, said terminal-block fitting including first
electrical terminals arranged for removable and replaceable
connection from said first compartment when said terminai-block
fitting is mounted to said wall member, and
B. wherein said printed circuit board further comprises second
electrical terminals arranged for removable and replaceable
connection with said first terminals of said terminal-block
fitting.
34. Housing apparatus according to claim 32 in which said mounting
housing includes electrical feed-through connections formed between
said first and second opposed sides of said mounting housing, said
feed-through connections being in electrical circuit communication
with said printed circuit board by way of said second side of said
housing, and arranged to provide electrical circuit communication
between said printed circuit board and said second cavity by way of
said first side of said housing when said first circuit assembly is
mounted in said second compartment.
35. Housing apparatus according to claim 34
A. in which said second mounting seat comprises a radially
extending shoulder on said tubular wall, and a smooth inner surface
on said tubular wall extending circumferentially around said second
compartment and extending axially along said first axis from said
shoulder at least part way toward said second end of said body,
and
B. in which said mounting housing includes a collar extending
circumferentially around the periphery of said first side of said
mounting housing and extending axially along an axis normal to said
first surface, said collar including means for forming said second
pressure seal between said collar and said smooth inner surface,
said collar further including mounting means for removably and
replaceably seating a third element with a third pressure seal to
divide said second cavity axially into a first portion containing
said first circuit assembly and a second portion.
36. Housing apparatus according to claim 35 further comprising a
second circuit assembly removable and replaceable relative to said
second cavity by way of said second open end and having a mounting
portion for removably and replaceably mounting to said mounting
means of said collar with said third pressure seal.
37. Housing apparatus according to claim 36 in which said mounting
means of said collar comprises a plurality of radially-extending
first members circumferentially spaced in said collar, and said
second circuit assembly comprises a mounting bezel having a
corresponding plurality of radially-extending second members for
removably and replaceably interfitting with said plurality of first
members in said collar.
38. Housing apparatus according to claim 36 in which said second
circuit assembly comprises,
A. a mounting bezel having first and second opposed sides and a
through aperture between said first and second sides
B. a display mounted to said second side of said mounting bezel and
visible from said first side by way of said through aperture,
and
C. at least one printed circuit board mounted on said second side
of said mounting bezel and having first and second opposed sides,
said first side abutting and in electrical communication with said
display, said second side of said printed circuit board including a
set of electrical terminals in circuit communication with said
first side of said printed circuit board and said display, for
removable and replaceable connection with said set of electrical
feed through connections in said first circuit board assembly.
39. Housing apparatus according to claim 1
A. in which said body forms said first compartment with a tubular
wall extending axially along said first axis to said first end of
said body and
B. further comprising one or more through fittings in said tubular
wall, each of said through fittings communicating with said first
compartment.
40. Selectively pressured housing apparatus for electrical
elements, said housing apparatus having a body having a chamber
therein extending along a first axis, said body being open at a
first axial end and at a second axial end, and having a port
extending along a second axis transverse to said first axis, said
port communicating with said chamber, and at least a first end-cap
for removably and replaceably closing one said end, said apparatus
having the improvement comprising
A. a wall member inside said body extending transverse to said
first axis and parallel to said second axis and dividing said
chamber into first and second compartments axially spaced along
said first axis, said port communicating with said chamber at said
second compartment,
B. a first mounting seat in said second compartment for removably
and replaceably seating an electrical element received into said
chamber at said second open end,
C. an aperture extending through said wall member and communicating
between said first and second compartments, and
D. a second mounting seat on said wall member and extending
circumferentially about said aperture for removably and replaceably
seating, with a first pressure seal to said wall member, an element
received into said chamber at said first open end.
41. Housing apparatus according to claim 40 further comprising
A. a first circuit assembly removable and replaceable relative to
said second compartment by way of said second open end and having a
mounting portion removably and replaceably seated within said
second compartment,
in which said first circuit assembly and said second compartment
have mating mounting-seat means for engagement, upon mounting of
said circuit assembly in said second compartment, for forming a
second pressure seal between the portion of said second compartment
interior of said circuit assembly and the portion thereof exterior
to said circuit assembly, and
B. pressure release means on said first circuit assembly for
maintaining said second pressure seal and, alternatively, for
venting said second pressure seal to facilitate installation mad
removal of said circuit assembly relative to said second
compartment.
42. Housing apparatus according to claim 40 further comprising a
first circuit assembly removable and replaceable relative to said
compartment by way of said second open end and having a mounting
portion removably and replaceably seated within said second
compartment, said first circuit assembly having at least one
manually-engageable projection extending longitudinal to said first
axis, for manual removal and installation of said circuit assembly
in said second compartment by way of said second open end.
43. Housing apparatus according to claim 42 in which said first
circuit assembly has a pair of projections spaced apart along an
axis transverse to said first axis and longitudinal to said second
axis said pair of projections extending along said first axis
toward said second end of said body and forming a pair of opposed
manually engageable surfaces for the removal and alternative
installation of said first circuit assembly relative to said second
compartment.
44. Housing apparatus according to claim 1 in which said body forms
said second compartment with a tubular wall extending axially along
said first axis to said second end of said body, said apparatus
further comprising,
A. a second mounting seat in said second compartment for removably
and replaceably mountingly seating a second element with a second
pressure seal to said second mounting seat for dividing said second
compartment axially into a first cavity containing said port and a
second cavity,
B. a first circuit assembly removable and replaceable relative to
said second compartment by way of said second open end and having a
mounting portion removably and replaceably seated with said second
mounting seat, for selectively mounting said first circuit assembly
relative to said second mounting seat with said second pressure
seal between said first and second cavities,
said first circuit assembly having a handle-like projection
extending along said first axis towards said second end of said
body and manually engageable for installation and alternatively
removal of said first circuit assembly from said second
compartment.
45. Housing apparatus for.eleCtrical elements comprising
A. a body having a chamber therein extending along a first
axis,
B. a wall member inside said body extending transverse to said
first axis and dividing said chamber into first and second
compartments axially spaced along said first axis,
C. an aperture extending through said wall member and connecting
said first and second compartments, and
D. a mounting seat on said wall member and extending
circumferentially about said aperture and projecting along said
first axis into said first compartment from said wall member to
form, in said first compartment, a channel having a depth extending
along said first axis and extending circumferentially around said
mounting seat.
46. Housing apparatus according to claim 45 further comprising a
terminal-block fitting removable and replaceable from said first
compartment, and having a mounting portion for removably and
replaceably seating with said mounting seat, for selectively
mounting said terminal-block fitting relative to said wall
member.
47. Housing apparatus according to claim 46 in which said
terminal-block fitting includes a selected set of electrical
terminals arranged for removable and replaceable connection, with
electrical conductors, from said first compartment when said
terminal-block fitting is mounted to said wall member, and in which
said channel is adapted for storing an excess portion of said
electrical conductors.
Description
BACKGROUND OF THE INVENTION
This invention relates to housings for electrical elements. More
specifically, the invention provides an improved housing for
process electronics associated with a measuring or sensing device,
such as a differential pressure transmitter.
Differential pressure transmitters are commonly used in process
control systems that require pressure, flowrate, or measurements of
other variables associated with gases and liquids. One typical
prior differential pressure transmitter employs a two-section
housing assembly. A lower section of the transmitter assembly
communicates with an upper section of the transmitter assembly by
way of a port extending between the two sections.
The lower section typically houses, among other components, two
process diaphragms and a transducer. The lower section includes two
process fluid ports for coupling to input process lines for
exposing each process diaphragm to one of two fluid pressures that
are to be compared. Each process diaphragm deflects in response
to,the pressure of one fluid. The transducer responds to the
difference between the two pressures of the process fluids, and
produces electrical output signals for indication or control.
The upper section typically houses process electronics, i.e.
electronic circuits and electrical components for monitoring and
conditioning the electrical output signals from the transducer for
transmission to a display meter, and/or for application to a
control valve, a computer or another electronic device. In the case
where the conditioned signals are to be applied to a computer or
other electronic device, they can be coupled out of the second
section of the housing assembly, by way of fittings to electrical
conduits.
Typical process fluids can be corrosive and/or toxic. Accordingly,
the upper section of the housing assembly, which contains the
process electronics, is isolated from the process fluids that are
coupled to the lower section of the housing assembly. Since the
process fluids are only applied to one side of each process
diaphragm, the two process diaphragms and lower section of the
housing assembly form a chamber that is isolated from the process
fluids and is generally filled with an inert fill fluid.
Additionally, this chamber leads to a transducer for generating the
electrical output signals to the process electronics.
One disadvantage of some prior fluid measuring systems of the
foregoing type is that if either process diaphragm fails, the
process fluid can displace the inert fill fluid and the corrosives
or volatiles may eventually vent throughout the upper section of
the housing assembly, destroying the process electronics.
Additionally, the process fluids can then vent from the second
section through the electrical conduits, by way of the fittings in
the housing assembly. This can be especially dangerous if the
process fluids are toxic or flammable. Some prior housing
assemblies address this problem by providing a barrier wall that
divides the second section into two compartments; one containing
the port for communicating between the first and second sections of
the housing assembly and the other containing the fittings that
couple to the electrical conduits.
Nevertheless, these prior systems continue to suffer from several
drawbacks. For example, some employ hard-wired electrical
penetrators to feed signals through the barrier wall, and
consequently suffer from reduced flexibility with regard to
allocating circuitry between the two compartments. Others require
that an opening through the barrier wall in the second section be
either custom cast or custom machined. Still others have reduced
access to the circuitry housed in the second section.
Another drawback to some prior systems is that the two chambers
that are created by the barrier wall are not environmentally
controlled. Since one chamber is in communication with the lower
housing section by way of the port, the process electronics and
part of the lower housing section are exposed to any humidity
present in the chamber. Hence, some prior devices require all of
the electronic components in the upper section of the housing
assembly to be sealed or coated from ambient moisture, typically by
being potted or conformally coated with a moisture barrier. This
can be expensive and can complicate access to the components during
maintenance and repair.
In most differential pressure transmitters, the upper section of
the housing assembly is accessible at two axial ends by way of
threaded covers. While these assemblies provide access to the upper
section of the housing assembly, they may have significant
disadvantages. One such disadvantage arises because the prior art
assemblies typically provide only two compartments in the upper
section. Thus, if a cover is removed, all of the electronics housed
in that compartment are exposed to the outside environment. Hence,
operation in a humid environment can, once again, require the
circuits contained in the upper section to be sealed from moisture.
Another disadvantage is that such covers allow unrestricted access
to the electronics. Thus, the instrument can be inadvertently
damaged or subjected to tampering.
It is accordingly an object of this invention to provide an
improved housing assembly for process electronics that precludes
process fluids from venting into the electrical conduits, upon a
failure of one or both process diaphragms.
Another object is to provide a housing assembly that provides
improved flexibility with regard to arranging process electronics
in the housing, while still ensuring that process fluids are
blocked from the electrical conduits.
It is also an object of the invention to provide an improved
housing assembly that can contain various types of process
electronics, without modifications to the housing.
A further object of the invention is to provide a housing assembly
that has improved access, and yet is tamper-resistant.
An additional object of the invention is to provide a housing
assembly that minimizes environmentally infiltration while
eliminating the need for seal-coating the process electronics, by
potting or otherwise.
Yet another object of the invention is to provide a housing
structure that has relatively few parts and is relatively
economical to manufacture, and that can house a variety of
processing electronics, for varied commercial applications.
Other objects of the invention will in part be obvious and will in
part appear hereinafter.
SUMMARY OF THE INVENTION
The invention attains these and other objects by providing, in one
embodiment, a selectively pressured housing apparatus for
electrical elements. The housing apparatus has a body, a wall
member, an aperture, and a mounting seat. The body has a chamber
therein extending along a first axis, is open at a first axial end
and at a second axial end, and has a port extending along a second
axis transverse to the first axis. The port communicates with the
chamber. The wall member is inside of the body and extends
transverse to the first axis and parallel to the second axis and
divides the chamber into first and second compartments, which are
axially spaced along the first axis. The port communicating with
the chamber is in the second compartment. The aperture extends
through the wall member and communicates between the first and
second compartments. The mounting seat is on the wall member and
extends circumferentially about the aperture for removably and
replaceably seating an electro-mechanical element with a selected
pressure seal to the wall member. According to one preferred
embodiment, the first and second compartments house process
electronics associated with a differential pressure transmitter.
Accordingly, the port for communicating with the chamber can mount
to a second housing structure that contains process diaphragms, a
pressure transducer, and other components for coupling electrical
signals indicative of a differential pressure to the process
electronics.
According to a further feature of the invention, the mounting seat
projects axially along the first axis into the first compartment
from the wall member. A channel extends circumferentially around
the mounting seat and has a depth extending along the first axis.
The channel, can store a service loop of electrical wire, which can
be connected, for example, to the electro-mechanical element seated
to the mounting seat.
The mounting seat can have a variety of configurations. According
to one embodiment, the mounting seat includes a planar surface
facing along the first axis into the first compartment for
removably and replaceably seating the electro-mechanical element,
with a selected pressure seal, to the planar surface. In another
embodiment, the mounting seat has a finished surface, such as a
tubular surface, extending axially along said first axis. In one
preferred c6nstruction, the electromechanical element is mounted to
the mounting seat by way of the first compartment, and when
mounted, is disposed in the first compartment. The mounting seat
can further include fastening threads for the removable and
replaceable mounting of the electro-mechanical element. According
to one configuration, the fastening threads are formed in a
plurality of mounting holes axially extending into the mounting
seat. Alternatively, the fastening threads can be formed on a
plurality of mounting studs, axially projecting from the mounting
seat.
The electronics contained in the housing apparatus typically
require maintenance, repair, and calibration. Therefore, according
to one embodiment of the invention, at least one axial end of the
housing body is threaded for removable and replaceable assembly
with an end-cap for selectively closing that end of the body. In
apparatus including such an end-cap, it may be desirable to
regulate access. Consequently, according to a further feature, the
invention provides a tamper-resistant construction in which the
threaded end-cap has a substantially cylindrical outer surface,
with radial recesses therein spaced circumferentially about the
outer surface. The apparatus further includes a stem threadably
mounted on the housing body. The stem has a radially large portion
that selectively engages in one radial recess of the end-cap for
precluding rotation of the end-cap relative to the body. The stem
is mounted in a threaded aperture located adjacent to the end of
the body that mounts the end-cap. The threaded aperture extends
axially into the housing body along an axis parallel to the first
axis. The stem can mount in the threaded apeme so that the radially
large portion of the stem protrudes from the threaded aperture and
selectively seats in a radial recess in the end-cap. The threaded
aperture can also include a passage extending therethrough for
receiving a filament to engage a flatted portion of the stem to
preclude threading the stem, and thereby to lock it in place.
According to a further embodiment, the filament can be fastened to
preclude removal, thereby, limiting access to the electronic
circuitry within the housing.
According to a further embodiment of the invention, the port of the
housing apparatus includes a collar on the body and extending along
the second axis. The collar has a through passage for communication
with the second compartment, and has a tubular outer surface for
seating a label. The collar has a radial projection for fixing the
rotational position of the label.
Housing apparatus according to the invention can include an
electrical terminal-block fitting removable and replaceable
relative to the first compartment, by way of the first open end.
The terminal-block fitting has a mounting portion for removably and
replaceably seating with the mounting seat, for selectively
mounting the fittingrelative to the wall member with a selected
pressure seal between the first and second compartments. The
terminal-block fitting can include a selected set of first
electrical terminals arranged for removable and replaceable
connection from the first compartment when the terminal-block
fitting is mounted to the wall member. According to a further
feature, the terminal-block fitting includes a selected set of
second electrical terminals in electrical circuit communication
with the first electrical terminals and arranged for removable and
replaceable connection from the second compartment, when the
fitting is mounted to the wall member. In one preferred embodiment,
the electrical terminal-block fitting includes a terminal block and
a printed circuit board. The printed circuit board has first and
second opposed sides, and the first side mounts to the terminal
block. The circuit board carries the set of second electrical
terminals accessible for removable and replaceable connection from
the second compartment, by way of the aperture in the wall, when
installed.
According to another aspect of the invention, the second
compartment can be further subdivided. To this end, the second
compartment can include a second mounting seat for removably and
replaceably mounting a second electro-mechanical element with a
selected pressure seal. The mounted second element divides the
second compartment into first and second cavities. According to one
embodiment, the second element includes a mounting bezel, an
electrical display, and at least one printed circuit board. The
mounting bezel has first and second opposed sides and a through
aperture. The first side includes at least one axial projection
located on the periphery of the through aperture. The projection is
structured as a finger grip, to facilitate the removal and the
installation of the second circuit assembly by way of the second
open end. The display, which mounts to the second side of the
mounting bezel, is visible from the first side by way of the
through aperture.
The printed circuit board of the second electrical element has
first and second opposing sides and mounts to the second side of
the mounting bezel, with its first side in electrical communication
with the display. The second side of the printed circuit board of
the second electrical element can include electrical terminals that
are adapted for removable and replaceable connection with the
selected set of second terminals of the terminal-block fitting.
In a preferred practice of the invention, the selected pressure
with which the second electrical element is sealed to the second
mounting seat is less than the selected pressure seal formed
between the first and second chambers by the electrical
terminal-block fitting mounted to the first mounting seat. In this
way, in the unlikely event that any process fluid inadvertently
vents into the first cavity of the second chamber, created between
the terminal block fitting and the second electrical element, it
would later vent into the second cavity, rather than venting into
the first chamber.
According to an alternate embodiment of the invention, the second
electro-mechanical element includes a first circuit assembly that
has a mounting bracket and at least one circuit board. The mounting
bracket has first and second opposed sides, the first side having
at least one axial projection accessible as a finger hold for
installation and removal of the first circuit assembly relative the
second compartment, by way of the second open end. A plurality of
mounting supports project axially from and are spaced along the
periphery of the second side. Each mounting support includes one or
more lateral slots. A printed circuit board is adapted to interfit
with and engage one slot in each of the mounting supports to seat
the circuit board in the mounting bracket.
According to a further embodiment of the invention, the housing
apparatus can include both versions of the above described
electro-mechanical elements, each mounted in the second compartment
of the housing chamber. In this way, the second compartment is
subdivided into three cavities, each having a selected pressure
seal with respect to the others and with respect to the first
compartment.
The invention accordingly comprises the features of construction,
combinations and arrangements of parts exemplified in the
constructions hereinafter set forth, and includes the several steps
in relation to one or more other such steps for attaining such
constructions and combinations of elements, as exemplified in the
apparatus and the methods hereinafter disclosed, and the scope of
the invention is indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the
invention, reference is made to the following detailed description
and the accompanying drawing, in which:
FIG. 1A is a perspective view of a differential pressure
transmitter including a selectively pressured housing apparatus
according to the invention;
FIG. 1B is a perspective view of a locking stem of the type
employed in FIG. 1A to preclude rotation an end-cap;
FIG. 1C is a perspective view of a label of the type employed in
the apparatus of FIG. 1 A;
FIG. 2 shows a rear perspective partially cut away view of the
selectively pressured housing apparatus of FIG. 1A;
FIG. 3 is a rear perspective exploded view of the selectively
pressured housing apparatus of FIG. 1A;
FIG. 4 is a front perspective view, partially exploded, of the
selectively pressured housing apparatus of FIG. 1A;
FIG. 5 is a front perspective view, partially broken away, of the
selectively pressured housing apparatus of FIG. 1A;
FIG. 6 is a front perspective exploded view of the selectively
pressured housing depicted in FIG. 5;
FIG. 7 is an exploded front perspective view of the electronic
assemblies of the type depicted in FIG. 6; and
FIG. 8 is an exploded rear perspective view of the electronic
assemblies of the type depicted in FIG. 6.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
The present invention is directed to selectively pressured housing
apparatus that contain, for example, the process control
electronics for a differential pressure transmitter. Typically, as
in the illustrative embodiment described below, an upper housing
according to the invention couples to a second lower housing
containing, among other components, a pair of process diaphragms
and a pressure transducer. Each process diaphragm is exposed to one
of two fluid pressures that are to be compared, and deflects in
response to the pressure of that fluid. The transducer responds to
the difference between the two pressures of the process fluids, and
produces an electrical output signal that typically is used for
controlling fluid flow in process conduits. The electrical output
signal can be coupled to the process control electronics by way of
a port extending between the two housings. A lower housing adapted
for coupling to an upper housing according to the invention, is
described in further detail in U.S. patent application Ser. No.
08/294,090, filed in Aug. 22, 1994, assigned to the assignee of the
present application, and incorporated by reference herein.
Housing apparatus according to the invention can further include
one or more fittings connected to electrical conduits for coupling
processed signals, from the process control electronics, to other
electronic equipment, such as process controlling computers located
in remote control areas.
The housing apparatus of the invention provide several improvements
over the prior art. According to one feature, the invention
provides a housing assembly having multiple selectively pressure
sealed chambers. As detailed below, such selectively sealed
chambers ensure that process fluids do not inadvertently vent into
the electrical conduits, and improve environmental protection of
sensitive transmitter electronics. The invention, according to
another feature, provides a standard housing that can accommodate a
variety of customized circuit modules to provide any of multiple
functions at relatively low manufacturing and inventory costs.
Additionally, the invention provides improved access to the circuit
modules contained in the housing, and controls access to the
housing by way of a tamper-proof mechanism. These and other
features of the invention are detailed below.
FIG. 1A shows an external perspective view of a differential
pressure transmitter 100, including a selectively pressure sealed
housing assembly 102 according to the invention. As shown, the
illustrated upper housing assembly 102 is mounted on a second or
lower housing 104, which contains, among other components, a pair
of process diaphragms and a pressure transducer. Two process
fluids, whose pressures are to be compared, couple to the housing
104 and to the process diaphragms therein by way of fittings 106
and 108.
The housing assembly 102 includes a housing body 110 elongated
along a fixst axis 112 and having a collar 114 extending along a
second axis 116 transverse to the first axis 112. The body 110 has
a hollow inner chamber. To provide access to the inner chamber of
the body 110, the housing assembly 102 has removable and
replaceable end-caps 118 and 120, threadably mounted to axially
opposed open ends 122 and 124. Each end-cap 118 and 120 has a
substantially cylindrical outer surface that is recessed with
axially extending groove-like recesses 118a and 120a. The recesses
are spaced circumferentially about the outer surface of each
end-cap 118 and 120, to form radially-projecting flutes on each
end-cap. Any recess 118a on the end-cap 118 can selectively engage
a stem 126 to preclude rotation of the end-cap 118, with respect to
the housing body 110. Similarly, any recess 120a can selectively
engage a stem 128 to preclude rotation of the end-cap 120, with
respect to the housing body 110.
The illustrated stem 126, as shown in FIG. 1B, is structured as a
cylindrical machine screw with threads 126a, and has a flatted
portion 126b axially intermediate cylindrical portions 126c and
126d. The illustrated flatted portion 126b is generally
cylindrical, in transverse cross section, with a recess along a
chord.
Referring again to FIG. 1A, the housing body 110 includes a boss
130 having a threaded aperture 132, which extends parallel to the
first axis 112. To lock the end-cap 118 onto the body 110, to
preclude access, the threaded stem 126 seats in the correspondingly
threaded aperture 132, with the portion 126c protruding axially
from the aperture 132 to seat in a recess 118a. As shown, the
flatted portion 120b and other cylindrical portion 126d seat within
the threaded aperture 132. The housing body 110 is apertured at the
boss 130 with a hole 134 that passes through the threaded aperture
132. The hole 134 is located along the portion of the aperture 132
that seats the flatted portion 126b of the stem 126. A filament
136, such as a lock wire, passes through the hole 134 and engages
the flatted portion 126b to preclude rotation and removal of the
stem 126. The lock wire 136 can be fastened with a deformable clasp
138 to preclude inadvertent removal, thereby rendering the end-cap
118 relatively tamper-proof, unless the wire is cut. With the wire
136 removed, the stem 126 can be rotated and removed from the body,
or can be threaded further into the aperture 132 to be clear of the
end-cap flutes, to allow the end-cap 118 to be rotatably removed
from the body 110.
The stem 128, at the other end of the housing body, is constructed
in the same fashion as the stem 126. Accordingly, the illustrated
housing body 110 includes another boss 140 having an axially
extending threaded aperture 142. The stem 128 threadably seats in
the aperture 142 and includes a protruding portion that selectively
engages and seats in a recess 120a in the end-cap 120. A hole 144
passes through the aperture 142 to accommodate a lock wire 146,
which engages a flatted portion of the stem 128 to preclude
inadvertent removal thereof. Once again, a deformable clasp 147
fastens the wire 146 to precludes its unwanted removal.
With reference to FIGS. 1A, 1C, and 2, the housing assembly 102 has
a label 148 mounted circumferentially around a recessed outer
surface 115 of the collar 114. The label 148, shown in FIG. 1C,
includes a fastening tab 150, which upon installation of the label
on the collar 114, fits within a fastening aperture 152, and is
folded back to lock the label 148 onto the collar. Additionally,
the label 148 includes a notch or detent 154, which is formed when
the label 148 is fastened. The detent 154 interlocks with a radial
projection 156 on the collar 114 to fix the rotational position of
the label 148 on the collar 114. Thus, the detent 154, in
combination with the radial projection 156, provides a mechanism by
which the legend on the label can be selectively oriented on the
collar, without rivets or piercing the housing.
With further reference to FIG. 2, the illustrated body 110 of the
housing apparatus 102 has a boss 158 having a through fitting 160
that communicates through the tubular wall of the body to the
chamber. The fitting 160 can connect, with a conventional
structure, by means of an electrical conduit (not shown) to couple
electrical signals from the electronics within the housing body 110
to, for example, a remote control room. The fitting 160 is typical
of others that can be provided on the body 110; see for example the
further boss 159 and fitting 161, illustrated in FIG. 3.
With reference to FIGS. 2 and 3, the housing body 110 has a tubular
wall 162 that in part defines the chamber therein. A wall member
164 extends radially inward from the tubular wall 162. It is
oriented transverse to the first axis 112 and parallel to the
second axis 116. The wall member 164 divides the hollow chamber
into a user termination compartment 166 and an electronics and
display compartment 168; the compartments being adjacent along the
first axis 112. An apeme 170 extends through the wall member 164
and hence communicates between the two compartments. The aperture
170 has a mounting seat 172 circumferentially disposed about it for
removably and replaceably seating an electro-mechanical terminal
block fitting 174, with a pressure seal or deformable O-ring, to
the wall member 164. According to a preferred embodiment of the
invention, the electro-mechanical terminal-block fitting 174 is
removable and replaceable from the first compartment 166, by way of
the first open end 124.
As depicted in FIG. 3, the illustrated mounting seat 172 projects
axially along the first axis 112 into the user termination
comparUnent 166 from the wall member 164 to form an annular channel
176 between the axially projecting portion of the mounting seat 172
and the tubular inner wall 162. The channel 176 extends
circumferentially around the mounting seat 172 and provides a
storage area for electrical wires coupling signals out of the user
termination compartment 166 by way of fittings 160 and/or 161.
The illustrated mounting seat 172 includes a planar surface 178,
which faces along axis 112 into the first compartment 166. The
planar surface 178 is axially recessed with an O-ring groove 181. A
deformable O-ring which seats in groove 181 aids in achieving a
pressure seal between the terminal-block fitting 174 and the
mounting seat 172. The mounting seat 172 further includes tapped
holes 180a-180d for removably and replaceably fastening the
electro-mechanical terminal-block fitting 174 to the mounting seat
172 with bolts 198a-198d.
With reference to FIG. 4, the terminal-block fitting 174 includes a
terminal block 182 and a two-sided printed circuit board 184. The
terminal block 182 has a mounting portion with radial projections
186a-186d, each having a corresponding through holes 188a-188d.
Similarly, the printed circuit board 184 has a mounting portion
with radial projections 190a-190d, each also having corresponding
through apertures 192a-192d. A first side 182a of the terminal
block 182 includes a set of electrical terminals 194a-194h (FIG. 3)
for removable and replaceable connection from the user termination
compartment 166 and from conduit fittings 160 and 161. The
terminals 194a-194h electrically couple from the first side 182a of
the terminal block 182 to a corresponding set of solderable
terminals 196 on the opposed second side 182b of the terminal block
182.
During assembly, the through holes 188a-188d of the terminal block
182 are aligned with the through apertures 192a-192d of the circuit
board 184, and the first side 184a of the printed circuit board 184
is affixed to and seated flush with the second side 182b of the
terminal block 182. Electrical conductors on the circuit board are
electrically coupled to the terminals 194a-194h by way of the
solderable terminals 196. The terminals are soldered to the board
in a manner that closes any pre-existing through holes in order
that the board forms a seal barrier. In addition, terminals
194a-194h are blind holes so that the terminal block 182 also forms
a seal. Once the circuit board 184 is assembled with the terminal
block 182, the terminal-block fitting 174 (FIGS. 2 and 5), which
this assembly forms, can be secured to the mounting fitting 172. An
annular solder coated section 190e forms a seal seat for the O-ring
positioned in groove 181. According to a preferred embodiment, each
through aperture 188a-188d and 192a-192d axially aligns with a
corresponding tapped mounting hole 180a-180d, and the
terminal-block fitting 174 is secured in place by mounting bolts
198a-198d. When thus seated and secured, the fitting 174 with the
mounting seat 172 forms a pressure seal between compartments 166
and 168. One function of this pressure seal is to isolate humidity
or fluid present in compartment 166 from entering and damaging
electronics in compartment 168, shown in FIG. 6.
As shown in FIG. 4, second side 184b of the circuit board 184
includes a set of electrical terminals 200 for removable and
replaceable connection with process control electronics, contained
in the electronics and display compartment 168, by way of the
aperture 170. The circuit board 184 also includes EMI and RFI
protection circuitry. According to one embodiment of the invention,
a plurality of different circuit boards 184 and termination blocks
182, each having customized electrical functionality, can be
employed interchangeably in the housing apparatus 102. By way of
example, circuit board 184 can be adapted to couple various types
of conditioned signals to terminals 194a-194h, such as digital
signals or analog signals, in either optical or electrical form.
Additionally, a variety of terminal blocks 182, each having
customized terminal configurations, can be selected for employment
in the fitting 174, depending in part on the particular circuitry
contained on the circuit board 184. By way of example, the
terminals 194a-194f can be adapted as screw-type fittings, coaxial
cable connections, fiber optical connections, and/or banana jack
type connections. Additionally, those connections may or may not be
powered, and can provide digital or analog outputs. However,
regardless of the particular features of the selected terminal
block 182 or the selected circuit board 184, the terminal-block
fitting 174 maintains a consistent sealing function and mechanical
outline. Thus, a common housing body 110 can be employed,
regardless of the selected features of terminal-block fitting 174,
thereby reducing inventory and manufacturing costs.
With continued reference to FIG. 2, and additional reference to
FIGS. 5 and 6, the electronics and display compartment 168 (FIG. 6)
of the housing body 110 is adapted for removably and replaceably
seating first and second axially successive circuit modules 202 and
204, respectively, by way of the second open end 122. As shown, the
second compartment 168 is partially defined by an tubular wall 162.
The wall 162 has a threaded portion 208 (FIG. 6) for threadably
engaging the end-cap 118. The electronics and display compartment
168 also has a mounting portion for removably and replaceably
mounting the two axially successive circuit modules 202 and 204.
The illustrated mounting portion includes a finished, relatively
smooth cylindrical section 210, axially adjacent to the threaded
portion 208 and extending into compartment 168 along the wall 162.
The mounting portion 210 further includes, at its axially innermost
terminal end, a small shoulder 212 radially extending inward.
Mounting threads, comprising two threaded holes 214 and 216,
axially extend into diametrically opposed bosses 218 and 220, which
radially extend inward from the wall 162. The bosses 218 and 220
have planer surfaces 218a and 220a, respectively, facing along axis
112 into the compartment 168.
With reference to FIGS. 5 and 6, the first circuit module 202 of
the illustrated embodiment has a mounting bracket 222, two circuit
boards 224 and 226, and a receptacle 228. The circuit board 226
mounts inside receptacle 228, which can be filled with a potting
material to further seal electrical components on the circuit board
226, thus additionally protecting those components from
environmental adversities, such as humidity. The mounting bracket
222 removably and replaceably seats the circuit board 224, the
circuit board 226, and the receptacle 228. To this end, the
mounting bracket 222 is constructed from an electrically
insulative, flexible plastic. As shown in detail in FIGS. 7 and 8,
the bracket 222 has a first side 222a from which three axial
projections 230a-230c, equally spaced around its periphery, extend
along an axis normal to that side. Axial projections 230b and -230c
each includes two radially inward facing slots 232a and 232b, which
seat circuit boards. On one axial projection 230a, through
apertures 234a and 234b are used in lieu of slots. A tab 236 on the
circuit board 224 matingly interfits with the through aperture
234b, while the edge of the board 224 matingly interfits with the
slot 232b on each axial projection 230a-230c. Similarly, aperture
234a matingly receives a tab 238 on the circuit board 226. Radial
projections 228a and 228b on the potting receptacle 228 matingly
interfit with the slots 232a of axial projections 230b and 230c,
respectively. In this way, the bracket 222 secures the circuit
boards 224 and 226, and the potting receptacle 228, with a
removable and replaceable mounting. If potting is not required, two
printed wiring assemblies can, where desired, be accommodated in
place of the potting receptacle 228 and circuit board 226.
The mounting bracket 222 includes a collar 240 extending
circumferentially around and axially from an opposed second side
222b. The collar 240 includes four mounting notches 241a-241d for
optionally, matingly mounting the second axially successive circuit
module 204. Each mounting notch 241a-241d includes an axially
extending portion 243 and a circumferentially extending portion
245, shown in FIG. 6. The outer wall of the collar 240 seats a
deformable O-ring 242 circumferentially disposed around it. As
shown in FIGS. 6 and 7, the bracket 202 is apertured with two
diametrically opposed through holes 244a and 244b. As shown in FIG.
8, the surface 222a has two mounting pads 246a and 246b. Mounting
pad 246a is a flat finished surface that is circumferentially
disposed about aperture 244a. Similarly, mounting pad 246b is a
flat finished surface that is circumferentially disposed about
aperture 244b. During installation of the circuit module 202 in the
housing body 110, the surface 222b faces toward the open end 122
and is normal to the first axis 112. Each through aperture 244a and
244b axially aligns with one threaded aperture 214 and 216, shown
in FIG. 6. The module 202 telescopically interfits into the housing
body 110 so that mounting pads 246a and 246b seat flush on the
planar surfaces 218a and 220a, respectively. Threaded mounting
bolts 248 and 250 pass through the apertures 244a and 244b to
engage matingly threaded holes 214 and 216, respectively, to secure
the module 202 to the housing body 110. As shown in FIGS. 6 and 7,
the circuit board 224 includes notches 252a and 252b to enable the
mounting bolts 248 and 250 to pass, unobstructed. By securing the
mounting bolts 248 and 250, a pressure seal is formed between
planar surface 218a and mounting pad 246a, and between planer
surface 220a and mounting pad 246b, forming in combination with
O-ring 242 a sealed protected space for electrical circuit boards
224 and 226.
More particularly, as shown in FIG. 5, the O-ring 242 forms a
pressure seal with the finished portion 210 oft he tubular wall
162. Thus, the installed element 202 further subdivides the
electronics and display compartment 168 into first and second
cavities 256 and 258. The first cavity 256 extends axially from the
wall member 164 to the O-ring 242, and contains the circuit boards
224 and 226 and the potting receptacle 228. The second cavity 258
extends axially from the O-ring 242 to end 122 of the housing body
110. One advantage of this configuration, is that the end-cap 118
can be removed, without exposing the electronics of the module 202
to any adverse environmental conditions, such as, humidity.
Therefore, optionally, one or both of the circuit boards 224 and
226 can be constructed without additional moisture-sealing material
to protect the circuitry contained on those boards.
When installed in the compartment 168, due to the above discussed
selected pressure seals, the circuit module 202 can be difficult to
remove due to seal suction. Thus, as shown in FIG. 6, according to
another feai-ure of the invention, the surface 222b of bracket 222
includes two ribbed axial projections 260a and 260b for a
technician to grasp onto, when removing module 202 from compartment
168. These projections provide opposed and spaced-apart surfaces
for manual engagement from the open end 122 of the housing body
110. However, under certain atmospheric conditions, a vacuum can
develop in the first cavity 256, relative to the second cavity 258.
If such a vacuum forms, even the finger grips 260a and 260b can
prove insufficient to remove the module 202. Therefore, according
to a preferred embodiment of the invention, upon loosening the
mounting bolts 248 and 250, the pressure seal between the planar
surfaces 218a and 220a and the mounting pads 246a and 246b is
broken, thereby, releasing any vacuum so formed.
As shown in FIGS. 2 and 6, a port 276, through which electrical
connection can be made to a pressure transducer, communicates with
the first cavity 256 of the electronics and display compartment
168. In the event of a failure of one of the process diaphragms
associated with the pressure transducer, process fluids may after
an extended period of time vent into the cavity 256, shown in FIG.
2. As previously discussed, it can be dangerous for process fluids
to mix with the inert fill fluid and eventually cause corrosion
that might permit gas to vent into electrical conduits by way of
fittings 160 and 161. Thus, according to one feature of the
invention, the pressure seal between cavities 256 and 258 is
selected to be substantially less than the pressure seal between
the terminal-block fitting 174 and the mounting seat 172. By way of
example, according to a preferred embodiment, the seal between the
terminal-block fitting 174 and the mounting seat 172 can withstand
pressures of upwards of 800 psi, while the seal between cavity 256
and cavity 258 can only withstand pressures of about 3-5 psi.
Further, the seal, formed by end cap 118, between cavity 258 and
the external atmosphere, can only withstand pressures of
approximately 400 psi. Consequently, any such gases which vent into
cavities 256 and 258 would vent to the atmosphere, rather than
entering the conduits. Thus, if process fluid inadvertently vents
into the first cavity 256, the fluid vents into the second cavity
258, and then to atmosphere and does not rupture the seal between
the terminal-block fitting 174 and the mounting seat 172.
Turning to the electrical interconnections associated with circuit
module 202, as shown in FIGS. 7 and 8, the circuit boards 224 and
226, and the bracket 222 which mounts them, have a plurality of
electrical terminals for removable and replaceable connection. By
way of example, the circuit board 224 has a first electrical
connector 260 on the side 224a and has a set of associated
electrical terminals 260a that axially project from the opposite
side 224b. The circuit board 224 has a second electrical connector
262, mounted adjacent to connector 260 on side 224a, that also has
a set of associated electrical terminals 262a that axially project
from side 224b. The terminals 260a and 262a are adapted for
removable and replaceable electrical connection to other electrical
devices, namely to a differential pressure transducer in the
illustrated embodiment. The circuit board 224 further includes a
third connector 264 mounted on side 224a. The connector 264
removably and replaceably connects directly to a connector 266,
which is mounted on side 222a of the bracket 222. The connector 264
couples electrical signals through the bracket 222 to a connector
268 mounted on the bracket side 222b. The circuit board 224 has two
additional electrical connectors 270 and 272 mounted on side 224b.
The connector 270 is adapted for removable and replaceable direct
connection to a mating electrical connector 274 on side 226a of the
circuit board 226. The connector 272 is adapted for a removable and
replaceable ribbon wire (not shown) connection to a reed switch
connection positioned in the port chamber of the housing assembly
276 (FIG. 2).
With respect to the electrical functionality of the circuit module
202, according to one embodiment of the invention, the circuit
board 224 performs signal processing, while the circuit board 226
provides power to the circuit board 224. More specifically, the
illustrated circuit board 224 receives electrical signals, which
are indicative of a pressure difference between two process fluids,
from a pressure transducer by way of the terminals 260a and 262a.
The circuit board 224 performs an analog-to-digital conversion on
the received signals. It then digitally processes the converted
signals to compensate for nonlinearity and temperature-related
errors in the signals from the pressure transducer. The circuit
board 224 formats the processed signals for digital transmission,
and couples those digital signals to board 226 by way of connectors
270 and 274. Board 226 in tam couples the signals to the electrical
terminal-block fitting 174, by way of a connector 267 on side 226b
of the circuit board 226 and the terminals 200 on the
terminal-block fitting 174. The circuit board 224 can also couple
the processed digital signals into the cavity 258, by way of the
connectors 264 on the circuit board 224 and the connectors 266 and
268 on the bracket 222. The circuit board 226 also performs a
digital-to-analog conversion on the processed signals, and provides
the processed signals, in analog form, to the electrical
terminal-block fitting 174.
According to a further feature of the invention, the sealed housing
electronics assembly 102, shown in FIGS. 1A and 5, includes an
electrical display module 204 that operates in conjunction with the
circuit module 202. As shown in FIGS. 7 and 8, the illustrated
display module 204 has a bracket 280, a circuit board 282, and a
display element 284. The display bracket 280 is shaped generally
like a circular lid and has opposed sides 280a and 280b, with a
rectangular aperture 281 therebetween. A rectangular bezel-like
frame 286 extends around the periphery of the rectangular apeme 281
and projects axially from both side 280a and 280b.
The display element 284, which can, for example, be a liquid
crystal display, seats in the aperture 281 within the bezel-like
frame 286, and is readable from side 280a by way of the rectangular
aperture 281. As shown in FIG. 8, the display element 284 includes
two horizontally extending rows 290 and 292 of electrical contacts.
Each row of electrical contacts 290 and 292 provides addressable
interconnections to a plurality of display segments in the display
element 284. As shown in FIG. 7, the side 282a of the circuit board
282 has two rows 294 and 296 of correspondingly arranged electrical
contacts for coupling electrical control signals to the display
element 284 by way of the rows 290 and 292 of contacts,
respectively.
The display bracket 280 has a peripheral rim-like collar 298
extending axially from and circumferentially around the surface
280b. The circuit board 282 seats within the collar 298. Flexible
conductors 300 and 302, shown in FIG. 7, mount between side 282a of
the circuit board 282 and the display element 284. Each flexible
conductor 300 and 302 has a plurality of electrically conductive
filaments passing through it between its opposed sides 300a and
300b, and 302a and 302b, respectively. When assembled, the flexible
conductors 300 and 302 matingly sandwich between side 282a of the
circuit board 282 and the display element 284. The side 300a of the
flexible conductor 300 couples to the contact row 296 of the
circuit board 282. Similarly, the side 300b couples to the contact
row 290 of the display 284. In this way, the flexible conductors
couple electrical control signals between the rows of contacts on
the circuit board 282 and the rows of contacts on the display
element 284.
The illustrated circuit board 282 has four through apertures
304a-304d for mounting to the display bracket 280. During assembly,
the through apertures 304a-304d axially align with axially
extending threaded mounting apertures 306a-306d in the bezel-like
frame 288. Mounting screws 308a-308d engage the threaded apertures
306a-306d to fasten the circuit board 282 in place to compress the
flexible conductors to ensure secure and reliable electrical
connection between the circuit board 282 and the display element
284.
As also shown in FIGS. 7 and 8, the circuit board 282 has two push
button switches 310 and 312 mounted on side 282a. The two push
button switches 310 and 312 couple through apertures 315 and 317,
respectively, in the bracket 280 and are accessible from the end
122 of housing 110. Gaskets 314 and 316 provides a pressure seal
between the push button switches 310 and 312 and the frame 288. The
circuit board 282 further includes an electrical connector 283 for
removably and replaceably connecting with a feedthrough connector
268 on the bracket 222 of the circuit module 202.
As shown in FIG. 6, the collar 298 of the display bracket 280
includes four circumferentially equally-spaced radial projections
318a-318d, for mounting the display module 204 to notches in the
collar 240 of bracket 222. During assembly, each radial projection
318a-318d interfits with an axially extending notch portion 245,
shown in FIG. 6, of a corresponding mounting notch 241a-241d. The
element 204 can then be rotated clockwise so that each radial
projection 318a-318d engages a circumferentially extending portion
243 of the corresponding mounting notch 241a-241d. In this way, the
display module 204 mounts, removably and replaceably, to and
interlocks with circuit module 202. The display module 204 can
mount in any one of four rotational orientations with respect to
the element 202 so that display element 284 is readable, regardless
of the rotational orientation of the housing body 110. This is
possible since circuit board assembly 204 is connected to circuit
assembly 202 by a flexible ribbon connector (not shown).
The collar 298 of the display bracket seats a deformable O-ring 320
circumferentially disposed there around. When display module 204
mounts to circuit module 202, the collar 298 telescopically fits
into the collar 240, with O-ring 320 forming a pressure seal with
the inner wall of collar 240. The seal, thus formed,
environmentally isolates the electronics of circuit module 202 and
display module 204. Consequently, the end-cap 118 can be removed
and the push buttons 310 and 312 accessed, without exposing any
circuitry contained in that compartment to adverse environmental
conditions, such as excessive moisture.
Since the display module 204 is seated with a selected pressure
seal to the circuit module 202, it can be difficult to remove.
However, according to a further feature of the invention, two
ribbed manually-engageable tabs 322 and 324 axially project from
the surface 280a for a technician to grasp when removing, and when
installing, the display module 204.
In the foregoing embodiment, where the display module 204 is
employed with the circuit module 202, the latter module preferably
includes a power supply and signal processing circuitry, previously
discussed, and the circuit board 282 of the display module 204
contains circuitry for controlling and interfacing with the display
element 284, and with the push button switches 314 and 316. In
applications that do not require both modules, the display module
204 is used alone. The circuit board 282 then additionally includes
the signal processing and the power supply circuitry, in lieu of
the circuit boards 224 and 226. According to this alternative
embodiment, the display module 204 can, nevertheless, utilize a
bracket of similar construction to the circuit-board bracket 240 to
provide selected rotational orientations. However, in that case,
the circuit-board bracket need not include structures, such as the
axial projections 230a-230c, for mounting additional circuit
boards. According to one practice where the display module 204 is
used without the circuit module, the circuitry for providing
processed signals to the terminal-block fitting 184 in digital
format is omitted. In this way, the invention provides a plurality
of interchangeable circuit modules and display modules, which can
be utilized in a plurality of combinations to provide a variety of
selectable electrical features.
Regardless of whether the display module 204 is employed separately
or in conjunction with the circuit module 202, the push button
switches 310 and 312 operate in essentially the same manner to
enable a technician to perform various diagnostic and/or
calibration functions. By way of example, among other functions,
these switches can enable a technician to calibrate the electrical
elements and the pressure transducer with regard to a pressure
reference; alternate functions are to zero the system, initialize
the electronics, and to adjust the pressure span over which the
display element 284 operates.
As shown in FIG. 5, the end cap 118 is constructed with a
transparent window 326 for providing visual access to the display
element 284. The window 326 is seated with a selected radial
pressure seal to a shoulder 328 on the end cap 118, by way of a
deformable O-ring 330. A ring clamp 332 is compressed into a slot
334 to fasten the glass in place, with the selected pressure
seal.
It will thus be seen that the invention efficiently attains the
objects set forth above, among those made apparent from the
preceding description. Since certain changes may be made in the
above constructions without departing from the scope of the
invention, it is intended that all matter contained in the above
description or shown in the accompanying drawings be interpreted as
illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended
to cover all generic and specific features of the invention
described herein, and all statements of the scope of the invention
which as a matter of language might be said to fall there
between.
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